JAVASCRIPT

js get all indexes of value in array

// find all indexes in array that match value
let indices = array.map((e, i) => e === value ? i : '').filter(String)

get all indexes for element in array javascript

function getAllIndexes(arr, val) {
    var indexes = [], i;
    for(i = 0; i < arr.length; i++)
        if (arr[i] === val)
            indexes.push(i);
    return indexes;
}